Field of the Invention
The present invention relates to an optical apparatus that deforms the reflecting surface of a mirror, a projection optical system including the optical apparatus, an exposure apparatus, and a method of manufacturing an article.
Description of the Related Art
In order to improve the resolution of an exposure apparatus for use in manufacturing semiconductor devices, there is a need to correct the optical aberration of a projection optical system included in the exposure apparatus. Japanese Patent Laid-Open No. 2004-64076 proposes an optical apparatus that corrects the optical aberration of a projection optical system by applying a force to a mirror included in the projection optical system by a plurality of actuators so as to deform the reflecting surface of the mirror.
In an exposure apparatus, if vibrations of the floor on which the exposure apparatus is disposed, vibrations generated within the exposure apparatus, and the like are transmitted to the mirror as disturbance, the mirror may be deformed due to the vibrations. The optical apparatus disclosed in Japanese Patent Laid-Open No. 2004-64076 corrects such an unintended deformation of the mirror caused by vibrations by controlling each actuator based on the error between the mirror shape measured by a sensor and the target shape. With such control, however, each actuator is controlled based on the result of measurement of the shape of the mirror deformed by the vibrations transmitted to the mirror, which makes it more difficult to cause the control of each actuator to follow vibrations as the frequency of the vibrations increases. In other words, an unintended deformation of the mirror caused by vibrations having a high-frequency component may not be sufficiently corrected.